On Mon, Feb 27, 2023 at 11:26:17AM -0800, Darrick J. Wong wrote: > > As I wrote above, for metadata there ought to be something as otherwise it > > will be real pain (and no gain really). But I guess the concrete API only > > matterializes once we attempt a conversion of some filesystem like ext2. > > I'll try to have a look into that, at least the obvious preparatory steps > > like converting the data paths to iomap. > > willy's tried this. Well, I started on it. The first thing I looked at was trying to decide how to handle the equivalent of BH_boundary: https://lore.kernel.org/linux-fsdevel/20200320144014.3276-1-willy@xxxxxxxxxxxxx/ I'm no longer sure that's the right approach. Maybe we do want to have an IOMAP_F_BOUNDARY to indicate that the bio should be submitted before calling iomap_iter() again. But we're definitely still missing the piece where we start the I/O to the page by setting iop->read_bytes_pending to folio_size() and then subtract off each piece as we either zero it or the I/O completes. I have a bunch of other pagecache / fs work queued up for this cycle, so I wasn't planning on leaping back into this. But it's worth making sure hat people know about one of the problems we figured out three years ago: https://lore.kernel.org/linux-fsdevel/20200505190825.GB5694@magnolia/
